Recent penetration of solar power generation facilities among general households may cause increases in voltage, abnormalities in frequency, or the like in a power distribution grid (commercial grid) when a number of solar power generation facilities installed rises.
Therefore, a system is proposed for maintaining a voltage or a frequency in a power distribution grid at an appropriate value by distributed arrangement of lower-capacity power storage devices between a power distribution grid and consumers to absorb surplus power at solar power generation facilities by storage batteries.
More specifically, for example, a method is proposed for including a current injection unit that injects an injection current of non-integral multiple order of a fundamental wave in a power distribution grid into the power distribution grid and a proportional computing unit that computes, using a voltage and a current of an injection degree at a connecting point between a voltage-rise suppression device and a power distribution grid, a resistance (r1) and a reactance (x1) of a fundamental wave component in the power distribution grid at the connecting point and a ratio α1 (=r1/x1) between the resistance r1 and the reactance x1 to generate a reactive power command value from the ratio α1.
However, with a conventional method, an impedance in a power distribution grid is preliminarily measured and the measured resistance and reactance values are used for controlling active and reactive power. Therefore, an additional instrument for measuring an impedance is required, and for example, when a configuration of a power distribution grid is changed, it is necessary to measure an impedance again.